1. Field of the Invention
This invention relates generally to a light or a lighting device, such as a backlit graphic display device. More particularly, this invention relates to a backlit graphic display device for illuminating a graphics panel, which device can be positioned on or near a window or glass surface, such as on a vehicle.
2. Brief Discussion of Prior Art
Electroluminescent (EL) lamps or devices have been used for signage. There are known methods for manufacturing EL lamps or devices. One conventional emergency exit sign uses an EL lamp in combination with a pilot light which is connected to the EL lamp by way of a photoelectric link. The photoelectric link monitors the brightness of the EL lamp and keeps on the pilot light as long as the EL lamp is lit. Illumination provided by the EL lamp may be less than the illumination of background brightness, making it difficult to tell by looking at the EL lamp whether or not the EL lamp is energized. Thus, the pilot light provides a point of illumination that can be easier to detect than whether the EL lamp is lit. This particular combination can be useful for building inspectors that check the operational status of an exit sign.
Other prior art systems include U.S. Pat. No. 5,390,436 ('436 Patent), issued to Ashall, which '336 Patent discloses a Display System. The '436 Patent describes an edge-lit illuminated display system has a transparent medium having first and second opposing surfaces and at least one edge operable with a light source for illuminating the first and second surfaces, A matrix of dots on each of the surfaces is arranged to allow interaction of light between the surfaces. The matrix of dots on at least one of the surfaces substantially covers the entire surface for providing an even increased illumination throughout the surface, wherein when a graphic image is supported over the surface the graphic image is evenly illuminated.
U.S. Pat. No. 5,718,497 ('497 Patent), issued to Yokoyama et al. discloses a Surface Light Source Device. The '497 Patent describes a surface light source device comprising a light-conducting member consisting of a sheet of transparent material, a linear light source disposed adjacent to an edge surface of the light-conducting member, a diffusion plate disposed on a front surface of the light-conducting member and a reflective plate disposed on a rear side of the light-conducting member. The rear surface of the light-conducting member has depressions or projections. These depressions or projections have rough surfaces. By selecting the shape of the depressions or projections, and controlling the roughness of the rough surfaces, an enhanced uniform brightness distribution is provided.
U.S. Pat. No. 5,957,564 ('564 Patent), issued to Bruce, discloses a Low Power Lighting Display. The '564 Patent describes a lighting display comprising a plurality of electroluminescent lamps (ELs) connected in parallel across a rechargeable battery that is connected to the EL's through an inverter. A solar panel device recharges the battery. Electroluminescent lamps for use in light strings are produced by cutting decorative shapes from existing electroluminescent material and mounting them back to back, in receptacles connected to electric wiring as in conventional light strings. For greater protection and ease of use the lamps may be mounted inside a length of clear plastic tubing, or may be laminated within layers of plastic material.
U.S. Pat. No. 6,783,259 ('259 Patent), issued to Macedonia, discloses an Apparatus for Recreating and Illuminating a Visual Image. The '259 Patent describes an apparatus for recreating and simultaneously illuminating the visual features of a substantially planar visual image using illumination devices, the United States flag being a visual image utilized in one embodiment.
From a review of the foregoing and a consideration of the prior art in general, it will be understood that the prior art perceives a need for a backlit graphic display device for illuminating interchangeable graphic panels, the backlit graphic display device comprising a housing assembly, a light source assembly, a light guide assembly, and laterally opposed device-to-surface mount or retainer structures for fastening the graphic display device to a window wherein the device-to-surface retainer structures each comprise an edge-receiving void as substantially summarized and described hereinafter.